This Mentored Research Scientist Development Award (K01) application is intended to provide training in areas that will lead to a program of longitudinal research on externalizing psychopathology and inform preventive interventions for at-risk children and families. The training and research proposed in this application will build upon the candidate's background in emotion theory and research on the development of psychopathology in at-risk populations. In line with National Institute of Mental Health's current Strategic Plan, the candidate proposes training to fulfill the following goals: (1) to learn approaches in molecular and behavior genetics that can increase understanding of how genotype and environment operate together in the development of externalizing psychopathology; (2) to increase the candidate's understanding of sensitive periods in the development of emotion regulation and risk for externalizing psychopathology; and (3) to learn advanced techniques to measure and analyze emotion expression and emotion regulation, especially in situations that induce anger and frustration. Training activities will include intensive training in genetics, guided discussion of directed readings on two sensitive developmental periods (toddlerhood and adolescence), coursework and tutorials on coding of emotion and advanced analytic approaches for dyadic data, and attendance at scientific workshops and conferences. These activities will be applied in studies of the relations among parental risk, parent-toddler hostility and rigidity, and toddler emotion regulation and conduct problem outcomes. In Study 1, maternal emotion dysregulation will be examined among 100 low- income, adolescent mothers in relation to hostile and rigid parent-toddler interactions, and hostility and rigidity in interactions will be examined as predictors of early-starting conduct problems. In Study 2, the candidate will apply the genetics training to an investigation of similar processes in an ongoing longitudinal study of birth parents, adoptive children, and their adoptive families (the Early Growth and Development Study).